Reliable Axial Displacement Monitoring for Critical Machinery
The Bently Nevada 991-25-50-01-00 991 Thrust Sensor is a compact, two-wire, loop-powered thrust transmitter designed to continuously monitor shaft axial displacement (thrust position) in rotating machinery. Developed for OEM equipment and industrial process applications, the 991 Series converts signals from a compatible 3300 NSv proximity probe system into a precise 4–20 mA output, enabling seamless integration with PLC, DCS, SCADA, and machinery protection systems. Integrated Proximitor® electronics simplify installation by eliminating the need for an external signal conditioning module while maintaining accurate and dependable performance.
The 991-25-50-01-00 configuration features a 2.5 mm (2500 μm) full-scale axial displacement range, a 5-meter transducer system, 35 mm DIN-rail mounting, and a standard (no agency approval) configuration, making it suitable for compressors, pumps, turbines, motors, and other rotating equipment where continuous thrust monitoring is essential.
Technical Specifications
| Parameter | Specification |
|---|
| Manufacturer | Bently Nevada |
| Model Number | 991-25-50-01-00 |
| Product Type | 991 Thrust Sensor / Thrust Transmitter |
| Measurement Type | Shaft Axial Displacement (Thrust Position) |
| Full Scale Range | 2.5 mm (2500 μm) |
| Compatible Probe | 3300 NSv Proximity Probe |
| System Length | 5.0 m (16.4 ft) |
| Output Signal | 4–20 mA proportional output |
| Power Supply | 12–35 VDC |
| Loop Configuration | Two-wire loop powered |
| Mounting Method | 35 mm DIN-rail clips |
| Signal Conditioning | Integrated Proximitor® electronics |
| Diagnostic Outputs | PROX OUT and COM terminals |
| Maximum Loop Resistance | 1000 Ω at 35 VDC |
| Operating Temperature | -35°C to +85°C |
| Storage Temperature | -52°C to +177°C |
| Construction | Fully potted industrial enclosure |
| Dimensions | Approx. 100 × 74 × 53 mm |
| Weight | Approx. 0.43 kg |
Industrial Applications
The 991-25-50-01-00 is designed for continuous monitoring of shaft thrust position in demanding industrial environments.
| Industry | Typical Equipment |
|---|
| Oil & Gas | Centrifugal compressors, pipeline pumps |
| Petrochemical | Process compressors, expanders |
| Power Generation | Steam turbines, generators |
| Chemical Processing | High-speed rotating machinery |
| Manufacturing | Industrial motors, blowers, fans |
| OEM Equipment | Compressor and pump skids |
Typical applications include:
-
Axial shaft displacement monitoring
-
Thrust bearing protection
-
Machinery condition monitoring
-
Predictive maintenance programs
-
Equipment health diagnostics
-
PLC, DCS, and SCADA integration
Key Advantages
Wide 2.5 mm Measurement Range
The 25 full-scale option provides a 2.5 mm axial displacement range, making it suitable for applications requiring extended shaft movement monitoring.
Integrated Proximitor® Electronics
Built-in signal conditioning reduces installation time, minimizes wiring, and eliminates the need for a separate Proximitor module.
Flexible 5-Meter System Length
The 50 option includes a 5-meter transducer system, offering installation flexibility for machinery where the control cabinet is positioned away from the monitored shaft.
Simple DIN-Rail Installation
The 01 mounting option supports standard 35 mm DIN-rail installation, allowing quick integration into industrial control panels and OEM cabinets.
Industry-Standard 4–20 mA Output
The transmitter provides a linear 4–20 mA signal, ensuring compatibility with modern automation systems and simplifying machine condition monitoring.
Durable Industrial Construction
Its rugged, fully potted design withstands harsh industrial environments, helping ensure stable long-term operation and dependable performance.
Technical FAQs
1. What is the 991-25-50-01-00 used for?
It monitors shaft axial displacement (thrust position) and outputs a proportional 4–20 mA signal for machinery protection and condition monitoring.
2. Which probe is compatible with this transmitter?
It is designed to work with the Bently Nevada 3300 NSv proximity probe and its matching extension cable.
3. What does the "25" option represent?
It specifies a 2.5 mm full-scale axial displacement measurement range.
4. What does the "50" configuration indicate?
It identifies a 5-meter (16.4 ft) transducer system length.
5. What does the "01" mounting option mean?
It indicates 35 mm DIN-rail mounting for industrial control cabinets.
6. What does the final "00" code indicate?
The 00 option designates the standard configuration with no agency approvals required.
7. What output signal does this model provide?
It delivers a 4–20 mA proportional output corresponding to shaft axial position.
8. Does this model require an external Proximitor?
No. It incorporates integrated Proximitor® electronics, reducing hardware requirements and simplifying installation.
9. What supply voltage is required?
The transmitter operates from a 12–35 VDC loop-powered supply.
10. Which machinery commonly uses the 991-25-50-01-00?
Typical applications include centrifugal compressors, turbines, pumps, motors, and other rotating equipment requiring continuous thrust position monitoring.
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